JPH0490126A - Production of magnetic coating material - Google Patents

Abstract

PURPOSE:To obtain a magnetic coating material excellent in the dispersibility of magnetic powder by using a relatively heavy dispersion medium and disposing stirring disks with the interval of a specified range to the outside diameter of the stirring disk. CONSTITUTION:A rotary spindle 3 for which lots of disks 2 for stirring are juxtaposed to be fixed is disposed in the center part of a cylindrical vessel 1, and the stirring disks 2 are fixed in a manner that the interval of the disks to the outside diameter of the stirring disk 2 is ranged within 3/9 - 1.1/9. The vessel 1 is preliminarily charged with a dispersion medium 9 of 0.6 - 2.0mm particle size and 4.0 - 6.5g/cc specific gravity such as zirconia ceramic beads into which a magnetic coating material compsn. 4 is introduced and forcedly stirred with the centrifugal force of the rotating disks 2. Thereby, the dispersion efficiency is improved and the obtd. magnetic coating material has the excellent dispersibility of the magnetic powder.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses a large number of stirring disks installed in the vessel of a vertical sand grinder mill to control the magnetic coating composition supplied into the vessel. The present invention relates to a method of manufacturing a magnetic paint by efficiently mixing and dispersing it together with a dispersion medium.

[Conventional technology]

In general, magnetic paint is produced by supplying a magnetic paint composition consisting of magnetic powder, a binder component, an organic solvent, and other necessary components into a mixing tank together with dispersion media such as glass beads. For example, as shown in FIG. 3, a large number of stirring disks 2 are placed in a cylindrical vessel 1 at intervals of 4/9 of the outer diameter of the stirring disks. Using a vertical sand grinder mill installed in parallel to the rotating shaft 3, the magnetic coating composition 4 roughly mixed by a rough mixer 5 is passed through a valve 6 and a check valve 8 by a pump 7. After that, the specific gravity is 1.6.
It is produced by forcibly stirring with the centrifugal force of the stirring disk 2 together with glass beads 91 of ~3.0 g/cc.

However, if glass beads 91 with a specific gravity of 1.6 to 3.0 g/cc were used as the dispersion media,
Mixing and dispersion of magnetic coating compositions is still insufficient, and for this reason, relatively heavy dispersion media such as zirconia ceramic beads having a specific gravity of 4.0 to 6.5 g/cc have been used in recent years. (Unexamined Japanese Patent Publication No. 63-125297) [Problems to be Solved by the Invention] However, using relatively heavy dispersion media such as zirconia ceramic beads with a specific gravity of 4.0 to 6.5 g/cc, the conventional When the magnetic coating composition 4 is mixed and dispersed using the vertical sand grinder mill shown in FIG. Stirring disc 2
Since the dispersion medium does not rise up to the point where the upper stirring disk 2 rotates and does not contribute to dispersion, the magnetic coating composition cannot be efficiently mixed and dispersed.

[Means to solve the problem]

This invention was made as a result of various studies in view of the current situation.
By using dispersion media of ~6.5 g/cc and setting the interval between the stirring disks in the vessel in the range of 3/9 to 1.1/9 of the outer diameter of the stirring disk, the upper part of the vessel The present invention solves the problem of low dispersion efficiency, mixes and disperses a magnetic coating composition with high efficiency, and makes it possible to obtain a magnetic coating composition with excellent dispersibility of magnetic powder.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a description will be given with reference to drawings showing a vertical sand grinder mill used for manufacturing the magnetic paint of the present invention.

In Fig. 1, reference numeral 1 denotes a cylindrical vessel, and in the center of the vessel 1 is installed a rotating shaft 3 on which a large number of stirring disks 2 are arranged and fixed in parallel. They are arranged in parallel so that the outer diameter of the disk 2 ranges from 3/9 to 1.1/9.

Reference numeral 4 denotes a magnetic coating composition supplied into the vessel 1, and the magnetic coating composition 4 is supplied by roughly mixing the magnetic coating composition 4 by a rough mixer 5 through a valve 6,
This is done by pump 7 via check valve 8. A stirring disk 2 rotates together with dispersion media 9 such as zirconia ceramic beads having a particle diameter of 0.6 to 2.0 m and a specific gravity of 4.0 to 6.5 g/cc, which are supplied in advance into the vessel 1. Forced stirring is performed using centrifugal force.

This forced stirring causes shear stress due to the difference in flow speed between the stirring disk 2 and the magnetic coating composition 4, and the magnetic coating composition 4 is mixed and dispersed by this shear stress. Then, the mixed and dispersed magnetic paint composition 4 gradually rises in the vessel 1, and after the dispersion medium 9 is separated by the screen 10, it is taken out from the vessel 1 and becomes a magnetic paint.

Here, each of the stirring disks 2 for mixing and dispersing the magnetic coating composition 4 supplied into the vessel 1 has a narrower interval between each stirring disk 2 than before, with respect to the outer diameter of the stirring disk 2. Since it is set in the range of 3/9 to 1.1/9, the upward movement of the dispersion medium 9 during dispersion increases, and the dispersion medium 9 rises to the stirring disk 2 at the upper part of the vessel 1. Dispersion and mixing is also carried out by the rotation of the stirring disk 2, and the dispersion and mixing is performed more uniformly.

As shown in 2, it is preferable that the interval between each stirring disk 2 is in the range of 3/9 to 1.1/9 of the outer diameter of the stirring disk 2, and the interval between the stirring disks 2 is If the ratio is narrowed to 1/9 or less of the outer diameter of the stirring disk 2, the laminar flow of the magnetic coating composition 4 during mixing and dispersion will not occur, and the gap between the dispersion media 9 and the stirring disk 2 will be reduced. Dispersibility due to shear force is significantly reduced.

In addition, the interval between the stirring disks 2 is in the range of 3/9 to 1.1/9 with respect to the outer diameter of the stirring disk 2, and the vessel 1
When the stirring disk 2 is unevenly distributed below the magnetic coating composition 4, the magnetic coating composition 4 can be mixed and dispersed more efficiently.

In this way, when the magnetic coating composition 4 supplied into the vessel 1 is mixed and dispersed with the stirring disk 2, the dispersion media 9 which is simultaneously supplied into the vessel 1 and used has high wear resistance. Because high toughness is required,
Particle size is 0.6-2.0 mm and specific gravity is 6.5 g/cc
A lower specific gravity is preferable, and the lower the specific gravity, the more preferable results can be obtained. Such dispersion media include:
For example, the particle size is 0.6 to 2. O1ffi has a specific gravity of 4.
Zirconia ceramic beads of 0-6.5 g/cc are preferably used.

The magnetic coating composition 4 consists of magnetic powder, binder resin, organic solvent, and other necessary components, and the magnetic powder includes:
For example, 7-Fe2O, powder, Fe3O4 powder, Co
Containing 7-Fe, 03 powder, CO containing Fe, 04 powder, C
A wide range of conventionally known magnetic powders are included, such as ry powder, Fe powder, CO powder, Ba ferrite powder, and the like.

In addition, binder resins that are generally used in magnetic recording media include vinyl chloride-vinyl acetate copolymers, cellulose resins, polyvinyl butyral resins, urethane resins, polyester resins, and isocyanate compounds. Both resins are used.

Further, as the organic solvent, solvents suitable for dissolving the binder resin, such as cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, toluene, and tetrahydrofuran, can be used alone or in combination without particular restriction. Ru.

In addition, lubricants, abrasives, dispersants, antistatic agents, and other substances that are generally added to magnetic paints may be added as necessary.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 As shown in Figure 1, the capacity is 21! A vertical sand grinder mill is used in which six stirring disks 2 are arranged in parallel on a rotating shaft 3 at intervals of 3/9 of the outer diameter of the stirring disks 2 in a vessel 1 of . Average particle size is 1.0m
Then, the following magnetic coating composition was supplied at a feeding rate of 130 g/min with the filling amount of zirconia ceramic beads 9 having a specific gravity of 6.0 g/cc at 50% by volume, and the stirring speed of the stirring disk 2 was 6 m/sec. Mixing and dispersion was carried out at a cooling water temperature of 10'C, and this mixing and dispersion was repeated once to six times.

Next, the magnetic paint produced by repeating such mixing and dispersion 1 to 6 times is coated on a polyethylene terephthalate film with a thickness of 33 μm to a thickness of 4 μm after drying.
．． Coating to a thickness of 0 μm and drying to form a magnetic layer,
A magnetic disk was made by punching it into a disk shape.

Magnetic coating composition Metallic iron powder (coercive force 1530 Els 100 parts by weight Ted, BET specific surface area 50 I/g, saturation magnetization 125 emu/g) Vinyl chloride-vinyl acetate ruby 11 Nyl alcohol copolymer polyurethane resin 6.6 Trifunctional isocyanate compound 4.4 Alumina powder
I5 Isoamyl stearate 1
0〃Cyclohexanone 155〃Toluene 155〃Comparative Example 1 In Example 1, instead of using the vertical sand grinder mill used in Example 1, as shown in FIG. A magnetic paint was produced in the same manner as in Example 1, except that a vertical sand grinder mill was used, in which five stirring disks 2 of 4/9 of the diameter were installed in parallel on the rotating shaft 3. , created a magnetic disk.

Comparative Example 2 In Example 1, instead of the vertical sand grinder mill used in Example 1, as shown in FIG. A magnetic paint was produced and a magnetic disk was made in the same manner as in Example 1, except that a vertical sand grinder mill was used in which the stirring disks 2 were mounted in parallel to the rotating shaft 3.

The surface roughness Ra of each magnetic disk produced in each example and comparative example was measured using a stylus type surface roughness meter.

Figure 2 shows the results as a relationship between the number of times of mixing and dispersion of the magnetic paint and the surface roughness Ra. From these graphs, it can be seen that the magnetic disk obtained in Example 1 was different from that in Comparative Examples 1 and 2. It can be seen that, compared to the obtained magnetic disk, the surface roughness is smaller, the dispersibility of the magnetic powder is improved, and the surface smoothness of the magnetic layer is improved.

〔Effect of the invention〕

As is clear from FIG. 2, the magnetic disk (Example 1) obtained using the magnetic paint manufactured by the manufacturing method of the present invention is different from that obtained using the magnetic paint manufactured in Comparative Examples 1 and 2. Compared to a magnetic disk, the surface roughness of the magnetic layer is small, and therefore, according to the method for producing a magnetic paint of the present invention, the dispersion efficiency is further improved, and a magnetic paint with excellent dispersibility of magnetic powder can be produced. It can be seen that by using this magnetic paint, a magnetic recording medium with excellent surface smoothness of the magnetic layer can be obtained.

[Brief explanation of drawings]

Figure 1 is a schematic cross-sectional view of a vertical sand grinder mill of the present invention, and Figure 2 shows the surface roughness of magnetic disks produced using the magnetic paints obtained in Examples and Comparative Examples, and the surface roughness of the magnetic paints. 3 and 4 are schematic cross-sectional views of a conventional vertical sand grinder mill.

Claims (1)

[Claims] 1. In a vessel of a vertical sand grinder mill, a plurality of stirring disks are installed with a diameter of 3/9 of the outer diameter of the stirring disks.
The magnetic paint composition containing magnetic powder and binder resin is placed in parallel to the rotating shaft at intervals of 1.1/9 to 1/9, and has a particle size of 0.6 to 2.0 mm and a specific gravity. 4.0-6
．． A method for manufacturing a magnetic paint, characterized in that it is supplied together with 5 g/cc of dispersion media and mixed and dispersed by rotation of each stirring disk to produce a magnetic paint.Claim 2, wherein the dispersion media is zirconia ceramic beads. Method for producing magnetic paint according to 1.